1. Technical Field
The present invention relates to a developing system comprising a plurality of image carriers, a plurality of developing devices for developing electrostatic latent images formed on the plurality of image carriers with respective developers of different colors of which carrier is nonvolatile solvent, and a plurality of developer collecting means which are disposed at a plurality of positions to collect excess developers. The present invention also relates to an image forming apparatus using the aforementioned developing system and comprising an intermediate transfer member to which developed toner images are sequentially transferred at primary transfer sections corresponding to the plurality of image carriers and are superposed on each other and which carries and transports the superposed toner image, and an output device which transfers the superposed toner image at a secondary transfer section from the intermediate transfer member to a sheet on a feeding path and outputs the image.
2. Related Art
There have been proposed various wet-type image forming apparatuses capable of visualizing an electrostatic latent image by developing the latent image with a high viscosity liquid developer containing a liquid solvent and a toner as solid substance dispersed therein. The developer employed in the wet-type image forming apparatus is formed by suspending solid substance (toner particles) in an electrical insulating organic solvent (carrier liquid) such as silicone oil, mineral oil, or cooking oil. The toner particles are very fine, for example, of about 1 μm in particle diameter. By employing such fine toner particles, the wet-type image forming apparatus can form high quality images as compared to a dry-type image forming apparatus employing powder-type toner particles of about 7 μm in particle diameter.
The carrier liquid composing the developer has not only a function of preventing the toner particles of about 1 μm in particle diameter from scattering, but also a function of making the toner particles charged and making the toner particles uniformly dispersed, and also a function of facilitating the transfer of toner particles by electric field during development and transfer process. Though the carrier liquid is a necessary ingredient for the toner conservation, the toner transport, the development, and the transfer process as mentioned above, the carrier liquid adheres also to non-imaging regions and the excess carrier liquid after development may cause deterioration of transfer. Accordingly, such an operation is normally performed as to remove (squeeze) carrier liquid on the photoreceptor and the intermediate transfer member (see, for example, JP-A-2002-296918). In case of a wet-type image forming apparatus employing an intermediate transfer belt and further a secondary transfer belt, such a measurement for removing liquid developer (carrier and solid substance) adhering to the belt surfaces by cleaning blades is taken (see, for example, JP-A-2002-189354). As for recycling the developers, there have been proposed a recycling system comprising a plurality of developing devices which are disposed to selectively face a photoreceptor drum and a plurality of squeezing devices corresponding to the respective developing devices which are disposed downstream from the developing devices, wherein excess developers used for the development on the photoreceptor drum are squeezed by the squeezing devices and the excess developers collected by the squeezing devices are returned to the corresponding developing devices by circulating devices (see, for example, JP-A-2003-107913).